Turbomachine nozzle cover for reducing jet noise
View Patent ↗A cowl for a turbomachine nozzle, the cowl having a plurality of repeated patterns disposed circumferentially at a trailing edge, each pattern being asymmetrical about a midplane of the pattern containing a longitudinal axis of the cowl, and each pattern having a first portion inclined radially towards the inside of the cowl and a second portion inclined radially towards the outside of the cowl.
1. A cowl for a turbomachine nozzle, the cowl having a plurality of repeated patterns disposed circumferentially at a trailing edge, wherein each pattern is asymmetrical about a midplane of the pattern containing a longitudinal axis of said cowl, wherein each pattern comprises a first portion inclined radially towards the inside of the cowl and a second portion inclined radially towards the outside of the cowl, and wherein each pattern is in a shape of a quadrilateral having a base common with said cowl.
2. A cowl according to claim 1 , wherein the first portion of each pattern extends longitudinally over a distance that is greater than the distance over which the second portion of said pattern extends.
3. A cowl according to claim 1 , wherein the inclination distance of the first portion of each pattern is greater than the inclination distance of the second portion of said pattern.
4. A cowl according to claim 1 , wherein the inclination distances of the first and second portions of each pattern lies in the range 5% to 30% of the respective distance over which each of said portions extends longitudinally.
5. A cowl according to claim 1 , wherein the first portion of each pattern extends longitudinally over a distance greater than half the circumferential distance occupied by a pattern, and wherein the second portion of each pattern extends longitudinally over a distance that is less than half said circumferential distance occupied by a pattern.
6. A cowl according to claim 1 , wherein the patterns are fin-shaped.
7. A cowl according to claim 1 , wherein the patterns are disposed symmetrically about a vertical plane containing the longitudinal axis of the cowl.
8. A cowl according to claim 1 , wherein a gap is provided in the trailing edge of the cowl having no pattern in the vicinity of the zone where said cowl is connected to a support pylon.
9. A turbomachine nozzle including a primary cowl disposed about a longitudinal axis of the nozzle, and a secondary cowl disposed concentrically around the primary cowl, wherein the primary cowl is a cowl according to claim 1 .
10. A turbomachine including a nozzle according to claim 9 .
11. A turbomachine nozzle including a primary cowl disposed about a longitudinal axis of the nozzle, and a secondary cowl disposed concentrically around the primary cowl, wherein the secondary cowl is a cowl according to claim 1 .
12. A turbomachine nozzle including a primary cowl disposed about a longitudinal axis of the nozzle, and a secondary cowl disposed concentrically around the primary cowl, wherein the primary and secondary cowls are cowls according to claim 1 .
13. A cowl according to claim 1 , wherein said quadrilateral is delimited by four straight line segments.
14. A cowl according to claim 1 , wherein said quadrilateral has its two diagonals inside said quadrilateral.
15. A cowl according to claim 1 , wherein said quadrilateral has apexes opposed to said base, wherein said apexes correspond to respective longitudinal ends of the first and second portions of each pattern.
16. A cowl according to claim 1 , wherein two adjacent patterns are not mirror-images of each other.
17. A cowl according to claim 1 , wherein said quadrilateral has, in addition to said base in common with said cowl, three sides that form edges of said cowl.
18. A cowl according to claim 17 , wherein a first side and a second side of said three sides each forms an angle β relative to said longitudinal axis, wherein said angle β is within a range of 15° to 45°.
19. A cowl according to claim 18 , wherein said angle β is about 30°.
20. A cowl according to claim 18 , wherein a third side of said three sides, opposite said base, forms an angle Υ relative to an axis perpendicular to said longitudinal axis, wherein said angle Υ is within a range of 15° to 45°.
21. A cowl according to claim 20 , wherein said angle Υ is about 30°.
22. A cowl according to claim 17 , wherein said quadrilateral has rounded corners.
23. A turbomachine nozzle comprising a cowl according to claim 1 , wherein said nozzle is axially symmetrical in shape about said longitudinal axis of said cowl.